CC-87-061: Addition of Alternative Methods for Measuring Volume and Flow Rate in Method 6

The attached material appeared in the October 28, 1987 Federal Register [FR 52 (208) 41423-41430]. In it, EPA is allowing the use of critical orifices for volume and flow rate measurements as an alternative to a dry gas meter in Method 6, the reference method for SO2 emissions measurements for stationary sources.